Curvature Excitation Through Quantum Wilson Loops In Four-Derivative Gravity

In the n-dimensional Minkowski space-time, the graviton propagators of the (R + R-2 + (RRmuv)-R-muv + (RRmuVlambdatau)-R-muvlambdatau)-gravity are shown in arbitrary and harmonic coordinates systems by using the perturbative expansion of the metric density. We calculated expressions for the leading terms of the quantum Wilson loop using these propagators and showed that they do riot vanish. This implies the existence of the possible curvature excitation through the quantum Wilson loop in the gravity. We also discussed relations of the possible curvature excitations among (R+ R-2 + (RRmuv)-R-muv + (RRmuvlambdatau)-R-muvlambdatau)-gravity, (R + R-2 + (RRmuv)-R-munu)-gravity, (R + F-2)-gravity and R-gravity.